Yes, the black tea gives a brown tone indoors (it's more reddish in the sun than if you'd mixed henna and indigo). Use one or two bags.
I was worried at first about looking like Ronald McDonald if I used the tea, but it was all good. It's easier to steep tea and then mix it all up with conditioner and oil. (I'm a tea drinker anyway.) I only have a few grays, and they look like burgundy highlights. I plan on doing another henna with tea 2/6.
I don't bother using brewed coffee or indigo anymore.